Coated carbonaceous particles particularly useful as electrode materials in electrical storage cells, and methods of making the same

ABSTRACT

A process for the production of coated carbonaceous particles, and the coated carbonaceous particles produced thereby of which process comprises the steps of: providing particles of a carbonaceous material; providing particles of a carbonaceous material; providing a coating of a fusible, carbon residue forming material onto the surface of said particles; stabilizing the coated particles by subjecting said particles to an oxidation reaction using an oxidizing agent; subsequently carbonizing the coated particles; and, optionally thereafter graphitizing the coated particles. The coated carbonaceous particles find particular use in electrodes of electrical storage cells, especially rechargeable lithium ion storage cells.

[0001] The present invention relates to graphitic materials which areuseful as electrodes in batteries. More particularly the presentinvention relates to coated carbonaceous particles which find particularuse as electrode materials, as well as methods for the manufacture ofsaid coated carbonaceous particles.

[0002] Carbonaceous materials are widely used in electrical storagecells, also referred to as “batteries” due to their efficiency andreasonable cost. Various forms of carbonaceous materials are used. Onesuch carbonaceous material is graphite, which is known to be useful inrechargeable storage cells, also referred to as “rechargeablebatteries”. In a salient example, graphitic materials are known to beuseful as anode materials in rechargeable lithium ion, “Li-ion” storagecells. Li-ion cells are mainly used as the power sources in portableelectronic devices.

[0003] As opposed to other classes of rechargeable batteries, i.e.,e.g., nickel-cadmium and nickel-metal hydride storage cells, Li-ioncells are increasingly popular due to their relatively higher storagecapacity, and their easily rechargeable nature. Due to such higherstorage capacity per unit mass or unit volume, Li-ion cells may beproduced which meet specific storage and current delivery requirementsas they are smaller than similarly rated, nickel-cadmium andnickel-metal hydride storage cells. Consequently, Li-ion cells arepopularly used in a growing number of devices, i.e., digital cameras,digital video recorders, computers, etc., where small sized devices areparticularly desirable from a utility or consumer standpoint.Nonetheless, rechargeable Li-ion storage cells are not without theirshortcomings, certain of which are dependent upon their materials ofconstruction.

[0004] Popular types of Li-ion storage cells include electrodes formedof mesophase carbon micro beads (MCMB) or micronized mesophase carbonfiber (MMCF). However, both MCMB and MMCF are relatively expensive dueto relatively complex manufacturing processes required for thesematerials. Further types of Li-ion storage cells include electrodesformed of comminuted or milled graphitic materials which are derivedfrom purified natural graphite or synthetic graphite. While thesematerials exhibit satisfactory storage capacity, they unfortunatelyexhibit a low initial charging efficiency on their first cycle.Typically, the charging efficiency of these materials ranges widely,usually from as little as about 40% to as high as about 90%. It is knownthat the efficiency of these comminuted or milled graphitic materials isstrongly dependent upon the morphology of the comminuted or milledgraphitic particles. Due to their irregular nature, these pulvurentcomminuted or milled graphitic materials frequently suffer from a lowpacking density which also limits the density from any electrode formedtherefrom, which also limits the operating characteristics of arechargeable storage cell. Also, due to their irregular nature,processing these pulvurent comminuted or milled graphitic materials intoelectrodes is difficult. In such electrodes formed from pulvurentcomminuted or milled graphitic materials, it has been suggested thatpoor operating characteristics is in part attributable to the formationof a passive film on the surfaces of these pulvurent materials. Such afilm is frequently described in the art as being a solid electrolyteinterface (“SEI”). The formation of this SEI irreversibly consumes aquantifiable amount, frequently a significant amount of lithium ions(typically 15 to 50%) present in the cathode upon cell assembly or use.

[0005] Accordingly there exists a real and continuing need in the artfor improved materials useful in the manufacture of storage cells,particularly rechargeable storage cells which exhibit improved operatingcharacteristics. There also exist needs in the art for improved methodsfor the manufacture of improved materials useful in the manufacture ofsuch storage cells, as well as for improved storage cells containingsaid improved materials.

[0006] In one aspect the present invention provides graphitic materialswhich comprise coated carbonaceous particles, wherein the coating layeris formed of an oxidized, carbon residue forming material, which coatinglayer may be also graphitized. These coated carbonaceous particles areparticularly useful in the manufacture of electrodes in electricalstorage cells, particularly in rechargeable electrical storage cells.

[0007] A further aspect of the invention are free-flowing coatedcarbonaceous particles with substantially smooth coatings formed of anoxidized, carbon residue forming material, which coating layer may bealso graphitized.

[0008] In further aspects of the invention there are provided methodsfor the manufacture of such coated carbonaceous particles.

[0009] A still further aspect of the invention relates to the use ofsaid coated carbonaceous particles in electrical storage cells,particularly in rechargeable batteries.

[0010] In a yet further aspect of the invention there are providedmethods for the manufacture of electrical storage cells, particularlyrechargeable batteries which include said coated carbonaceous particles.

[0011] These and other aspects and features of the invention will becomeapparent from the following description of the invention and preferredembodiments thereof.

[0012] In one aspect the present invention provides processes for themanufacture of coated carbonaceous particles, which materials exhibitimproved operating characteristics when used as electrodes in electricalstorage cells, particularly in rechargeable electrical storage cells.Generally the process contemplates the steps of:

[0013] providing particles of a carbonaceous material;

[0014] providing a coating of a fusible, carbon residue forming materialonto the surface of said particles;

[0015] stabilizing the coated particles by subjecting said particles toan oxidation reaction using an oxidizing agent;

[0016] subsequently carbonizing the coated particles; and,

[0017] thereafter optionally, but preferably graphitizing the coatedparticles.

[0018] Preferably the process provides particles having a substantiallysmooth coatings.

[0019] Particles of carbonaceous material are required for the practiceof the invention. These may be obtained from a variety of sources,examples of which include pitches, petroleum and coal tar cokes,synthetic and natural graphites, soft carbons derived from organic andnatural polymers as well as other sources of carbonaceous materialswhich are known in the manufacture of prior art electrodes althoughthese sources are not elucidated here. Preferred sources of carbonaceousmaterials include calcined or uncalcined petroleum cokes, as well asnatural and synthetic graphite. Particularly preferred sources ofcarbonaceous materials include calcined and un-calcined, highlycrystalline “needle” cokes. Thus, preferred carbonaceous materials areeither graphitic or form graphite on heating to graphitizationtemperatures of 2200° C. or higher. Fine particles of such materials areconveniently provided by milling, crushing, grinding or by any othermeans which can be used to provide a pulvurent carbonaceous materialhaving particles of dimensions which are suitable for use in theformation of electrodes. Although the principles of the presentinvention are believed to be applicable to carbonaceous particles ofvarying sizes and particle size distributions, preferred carbonaceousparticles having average particle sizes of up to about 150 mm, morepreferably from about 5 mm to about 70 mm, and most preferably averageparticle sizes in the range of about 5 mm to about 45 mm areparticularly preferred. Further, it is preferred that within theseranges, the particle size distribution is preferably such that not morethan 10% of the particles are smaller than 5 μm, not more than 10% ofthe particles are larger than 60 μm; further it is still more preferredthat in addition to such a particle size distribution that the meanparticle size is 10 to 30 μm

[0020] According to a step of the inventive process, the carbonaceousparticles are provided with a fusible, carbon residue forming materialas a coating material. Preferred for use as the coating material arecarbon residue forming materials which can be reacted with an oxidizingagent. Exemplary useful coating materials include heavy aromaticresidues from petroleum, chemical process pitches; lignin from pulpindustry; phenolic resins, and carbohydrate materials such as sugars andpolyacrylonitriles. Especially preferred for use as coating materialsare petroleum and coal tar pitches, and lignin which are readilyavailable and have been observed to be effective as fusible, carbonresidue forming materials.

[0021] It is to be understood that the carbon residue forming materialmay be any material which, when thermally decomposed in an inertatmosphere to a carbonization temperature of 850° C. or an even greatertemperature, forms a residue which is “substantially carbon”. It is tobe understood that “substantially carbon” indicates that the residue isat least 90% wt. carbon, preferably at least 95% wt. carbon. It is alsopreferred that the carbon residue forming material form at least 10% andpreferably at least 40% and more preferably at least 60% carbon residueon carbonization, based on the original mass of the carbon residueforming material.

[0022] Any useful technique for coating the carbonaceous particles maybe used. By way of non-limiting examples, useful techniques include thesteps of: liquefying the carbon residue forming material by a means suchas melting or forming a solution with a suitable solvent combined with acoating step such as spraying the liquefied carbon residue formingmaterial onto the carbonaceous particles, or dipping the carbonaceousparticles in the liquefied carbon residue forming material andsubsequently drying out any solvent. Further useful techniques includeselective precipitation of a carbon residue forming material on thecarbonaceous particles which may be preferred in certain circumstances.

[0023] A further technique which may be used includes providing a drycoating of the carbon residue forming material onto the carbonaceousparticles such as by mixing or tumbling these materials until a coatingof the carbon residue material is provided on the surface of thecarbonaceous particles, after which the dry coating is then fused toprovide a coating upon the surface of the carbonaceous particles. Whileany of these coating techniques may be practiced, preferred methodsinclude those which provide a relatively uniform coating thickness ofthe carbon residue forming material on the carbonaceous particles andwhich minimize clumping or agglomeration of the coated particles. Theamount of the carbon residue forming material deposited on thecarbonaceous particles may also vary widely, and it is understood thatthis amount depends in part on factors including the uniformity of thecoating and the specific form and surfaces of the carbonaceousparticles. Although the amount of coating may vary from as little as 1%wt. to as much as 50% wt., expressed as the percentage of the mass ofthe coating relative to the total mass of the coated particles asmeasured by weighing the dry particles before and after coating,preferably the amount of coating ranges from about 2.5% wt. to about 25%wt., more preferably ranges from about 5% wt. to about 20% wt.

[0024] According to a further step of the inventive process, the coatingof the carbonaceous particles are rendered partly or completelyinfusible, preferably by oxidative stabilization. The coating of thecarbonaceous particles are stabilized by subjecting said particles to anoxidation reaction using an oxidizing agent under appropriate reactionconditions. Generally, only mild to moderate reaction conditions arerequired. Typically the oxidation reaction is satisfactorily performedby contacting the coated carbonaceous particles with an oxidizing agentat elevated temperatures or by contacting the coated carbonaceousparticles with an oxidizing agent at mild conditions and activating theoxidizing agent at elevated temperatures. Contact with the oxidizingagent can occur at ambient temperatures (approx. 20° C.) or atmoderately elevated temperatures, (up to approx. 400° C.). Activation ofthe oxidizing agent would typically occur at moderately elevatedtemperatures up to 400° C. Preferably, the temperature of the oxidationreaction is maintained below the instantaneous melting point of thecoating material, so to ensure that melting point of the coatingmaterial is not exceeded during the oxidation reaction.

[0025] The manner of practice of this step of the inventive process isunderstood to be dependent upon the form of the oxidizing agentutilized, which may be solid, liquid or gaseous under the reactionconditions. Likewise, various oxidation reaction processes and reactionconditions may be practiced and are considered to be within the scope ofthe present invention.

[0026] Wherein the oxidizing agent is a solid, it is required only thatthe solid oxidizing agent be placed in sufficiently intimate contactwith the coated carbonaceous particles such that, under appropriatereaction conditions, a satisfactory degree of oxidation is obtained.This is most effectively accomplished by forming a liquid solution ofthe oxidizing agent, applying this solution to the coated particles anddrying. When practical, it is preferred to apply the carbon residueforming material and oxidant coatings at the same time in a single step.Where necessary, the oxidizing agent can be brought to suitable reactionconditions in order to insure the initiation and success of an oxidationreaction. Such conditions may take place under ambient pressure andtemperature conditions (approximately 20° C., 1 atm) however, dependingupon the nature of the oxidizing agent, the nature of the coatingmaterial, as well as in part the nature and form of any reaction vesselwhich may be used for the oxidation reaction, it may be desirous tomodify the temperature and/or pressure, or both from ambient. Typically,elevating the temperature up to 400° C. facilitates the initiation andthe subsequent oxidation reaction, but in fact, any temperature up tothe degradation temperature of the coating material can be successfullyused. With regard to the nature of any reaction vessel, anyconventionally used reaction vessel or device can be used. With regardto the identity of solid oxidizing agents, by way of non-limitingexamples, these include: inorganic and organic oxidizers such as metaloxides and salts such as alkali nitrates and alkali sulfates such as arerepresented by MNO₃ and M₂SO₄, where M denotes an alkali metal, as wellas M′O_(x) where M′ represents a transition metal. Exemplary solidoxidizing agents further include inorganic salts such as sodium nitrate(NaNO₃) and organic salts, as well as those described in the followingexamples.

[0027] Where the oxidizing agent is a liquid, it is required only thatthe oxidizing agent be provided in a liquid form which is compatiblewith the coated carbonaceous particles. It is clearly contemplated thatthe oxidizing agent itself need not constitute 100% of the liquid, butrather that the oxidizing agent be provided as a solution, suspension,or other fluid which comprises an oxidizing agent or agents therein. Itis anticipated that when the oxidizing agent is supplied as a solutionor suspension, it may be desirable to include a drying step so to drythe coated particles. It is contemplated that the oxidizing agent, whenpresent in a liquid form, is also compatible with the coatedcarbonaceous particles namely, that any portion of the liquid does notact to undesirably degrade or solubilize the fusible, carbon residueforming material or for that matter, the carbonaceous particlesthemselves. By way of non-limiting example, exemplary oxidizing agentswhich are provided in a liquid form include various oxidizing acids suchas nitric acid, perchlorate acid, phosphorous acid, sulfuric acid, aswell as aqueous and non-aqueous solutions containing oxidizing saltssuch as peroxides and KMnO₄ Additional liquid oxidizing agents includeperoxides and aryl quinones, as well as those described in one or moreof the examples.

[0028] The nature of the condition of the oxidizing reaction is notcritical to the practice of the invention particularly wherein theoxidizing agent is in a liquid form. Rather, it is only required thatthe reaction conditions be appropriate to insure the oxidation of atleast a portion of the coating provided to the carbonaceous particlessuch that they form a stabilized coating thereupon. Any conventionalreactor, and appropriate reaction conditions can be used. As describedpreviously, with respect to solid oxidizing agents, the reactionconditions can take place at ambient temperature and pressureconditions, or may require different conditions depending upon thecoating, the nature of the carbonaceous particles, the reaction vessel,and of course, the nature of the oxidizing agent utilized. With regardto reactor vessels, stirred reactor vessels which are optionallypressurized are conveniently used.

[0029] Where the oxidizing agent is gaseous, again it is required onlythat this gaseous oxidizing agent be brought into sufficient intimatecontact with the coated carbonaceous particles under appropriatereaction condition in order to insure the oxidization reaction of thecarbon residue forming material. According to this aspect of theinvention, a gaseous oxidizing agent may be most convenient to use inmany circumstances due to the fact that under appropriate reactionconditions, good mixing and contact with the coated carbonaceousparticles is easily achievable. By way of non-limiting example,exemplary gaseous oxidizing agents include: oxygen, sulfur fumes,gaseous oxides and halogens. Preferred oxidizing agents include oxygen,nitrogen oxide gas, as well as, under certain conditions, air, which ofcourse includes an appreciable proportion of oxygen gas.

[0030] With regard to the reaction conditions required, wherein theoxidizing agent is gaseous, again, it is required only that suchreaction conditions be appropriate to insure the oxidization of thecarbon residue forming material which is present on the carbonaceousparticles. Under certain conditions, ambient pressure and temperaturemay be sufficient, but yet again as described with reference to theother forms of oxidizing agents described previously, it may beadvantageous to insure that slightly elevated temperatures and/orpressures, e.g., temperatures in the range of between 30° C.-400° C.and/or slightly elevated pressures, e.g., 1-10 atm. be established toinitiate or maintain the oxidation reaction. Again, it is understoodthat the appropriate reaction conditions are highly dependant upon thenature of the carbon residue forming material used to coat thecarbonaceous particles, the specific gaseous oxidizing agent, as well asthe reaction vessel itself. Useful reaction vessels are those whichnecessarily can contain, or bring into contact, the gaseous oxidizingagent with the coated carbonaceous particles and while many conventionalvessels can be used, the use of the fluidized bed reactor is preferred.Utilization of a fluidized bed reactor wherein the gas flow streamcomprises the gaseous oxidizing agent is preferred as effective intimatecontact between the gaseous oxidizing agent and the coated carbonaceousparticles are reliably assured.

[0031] According to a further step of the inventive process the reactedcoated carbonaceous particles are subsequently carbonized andgraphitized. The coated and stabilized carbonaceous particles are heatedto a desired temperature in a suitable atmosphere so to be carbonizedand graphitized. The temperature range for the carbonization istypically between 550° C. and 1500° C. but can extend up to 2200° C.,and for graphitization is greater than 2200° C., preferably greater than2800° C.

[0032] According to this further step, heating of the coated andstabilized carbonaceous particles takes place under appropriate reactionconditions in order to insure a high degree, or a complete carbonizationthereof. With regard to the temperature required to insurecarbonization, desirably this is achieved by raising the temperature ina controlled manner from a starting temperature, usually ambienttemperature, to the final carbonization temperature which typicallyfalls within the above-identified range of about 550° C.-1500° C.

[0033] With regard to the temperature rise, this can vary due to thenature of the reacted coated carbonaceous particles, as well as thereaction conditions and apparatus used. With regard to the apparatus,typically conventional ovens are quite satisfactorily used, although itis preferred that sealed ovens wherein a specific atmosphere can bemaintained during the carbonization process are used. Sealed ovenswherein a reduced pressure may be maintained, especially vacuum ovensare particularly advantageous. With regard to the atmospheric conditionsfor the carbonization process, the atmosphere may be ambient air up toabout 850° C. but an inert atmosphere is preferred at temperatures aboveabout 400° C. Suitable inert atmospheres include nitrogen, argon,helium, etc. which are non-reactive with the heated coated carbonaceousparticles.

[0034] With regard to the temperature conditions, these can vary widelybut generally, the rate of temperature rise to which the reacted coatedcarbonaceous particles are subjected in order to achieve carbonizationthereof is on the order of 0.5° C.-20° C./min. Such a controlledtemperature rise insures that good carbonization results are achieved.Preferably however the coated carbonaceous particles are heated to afinal carbonization temperature gradually, and with at least oneintermediate heat treatment step where prior to the final carbonizationtemperature used in a process, the coated carbonaceous particles areheated to an intermediate temperature, and maintained at thatintermediate temperature for an interval of time. The intermediatetemperature or the period for which such intermediate temperature ismaintained may vary, and will be understood to depend from process toprocess. It is to be understood that the inclusion of one or more suchperiods of time during which the particles are maintained at suchintermediate temperatures is beneficial in facilitating thepolymerization or other ordering of the coating present on thecarbonaceous particles. Indeed, the practice of several suchintermediate heat treatment steps is further preferred over the practiceof a single heat treatment step in that the provision of more than oneheat treatment steps in which the coated particles are maintained at aconstant temperature is believed to impart improved characteristics tothe coated carbonaceous particles over particles which have undergonebut one or no such heat treatment step. It is further to be understoodthat during the heating of the coated carbonaceous particles particularattention must be paid to ensure that neither the temperatures attainedduring this heating process, nor the rate of the temperature rise duringany part of the heating process be such that the instantaneous meltingpoint of the coating upon the carbonaceous particles is exceeded. Moresimply stated, the thermal degradation of the coating is to be effectedby a controlled temperature rise wherein the process temperature ismaintained at or below the instantaneous melting point of the coatingwhere said melting point is generally increasing with time during theprocess. In view of this requirement, preferred heating processes arethose which exhibit slower rates of temperature rise. Particularpreferred examples of such heat treatment steps are described withreference to one or more of the Examples.

[0035] Subsequent to the attainment of the maximum temperature use forthe carbonization process, the carbonaceous particles having acarbonized coating may be cooled to ambient temperature, although thisis not an essential requirement. Again, the cooling rate is desirablycontrolled, i.e., to be within about 3° C.-100° C./min. although, thiscooling rate has been observed to be typically far less limiting thanthe rate of temperature rise during the carbonization process.

[0036] The most preferred aspects of the invention result in theprovision of a smooth coating upon individual carbonaceous particles.Preferably the stabilization of the coating is followed by controlledheating of the coated stabilized particles so as to effect carbonizationof the coated particles with little or no clumping or self-adhesion ofthe individual particles. The desired results are coated particles withlittle or no broken fracture surfaces of the type which arecharacteristically form when the separate particles fuse and must becrushed or broken apart in order to provide a free flowing powder. Suchfracture surfaces are desirably minimized or avoided as they arebelieved to contribute to low electrochemical efficiency when theparticles are used as an anode material in rechargeable electricalstorage cells, particularly in rechargeable lithium ion batteries.

[0037] According to a particularly preferred embodiment of the inventiveprocess taught herein, the carbon residue forming coating is provided ina fluid form. It has been observed by the inventors that when the carbonresidue forming coating is precipitated from a liquid, a smooth coatingforms at the interface of the individual carbonaceous particles and withthe surrounding liquid, smooth coating is retained when subsequentlycarbonized.

[0038] Although less advantageous, when the carbon residue formingcoating is supplied as a solid, it is desirably fused on the surface ofthe carbonaceous particles in order to form a smooth coating thereon.

[0039] The stabilization step of the current invention is carried out torender the surface of the coating infusible to the subsequentcarbonization step. Oxidative stabilization allows the smooth surfaceproduced in the coating process to be preserved in the final coatedparticles of the instant invention, as the oxidative stabilizationrenders the surface of the coating infusible to the subsequentcarbonization step.

[0040] Heat treatment of the stabilized coated particles is desirablyconducted in a controlled manner in order to minimize fusion of theparticles. One skilled in the art will recognize that highly stabilized,completely infusible coated particles can be heated relativelyaggressively and quickly during carbonization. In contrast, relativelymildly stabilized coated particles require slower heating in order toavoid excessive melting of the coating and fusion of the particles. Useof a fluidized bed during stabilization and heat treatment is especiallybeneficial in preventing clumping and fusion of the coated particles.

[0041] Especially Preferred embodiments of the present invention producea free-flowing powder of coated particles after the carbonization and/orgraphitization steps, which particles exhibit little or no fusion amongthe particles, but can generally be broken into a free-flowing powder bysimple mechanical agitation, such as by use of a stirring rod, or byrubbing between the thumb and forefinger. Where some fusion may haveoccurred between particles, and mechanical agitation is used to separatethese particles which may result in the formation of new fracturesurfaces, in the preferred embodiments of the invention these fracturesurfaces do not comprise more than 10%, preferably no more than 2% ofthe total surface area of the particles. Such are considered as beingsubstantially smooth coatings.

[0042] While it is preferred that the carbonized coated carbonaceousparticles be graphitized before use, graphitization is not essential asthe carbonized coated carbonized particles by the inventive process maybe used in various applications, including in the formation ofelectrodes, particularly anodes in batteries, especially in rechargeablebatteries. Preferably however, the carbonized coated carbonaceousparticles are also graphitized by heating them to a still higherelevated temperature which is in excess of the temperatures reachedduring the carbonization step. The advantage of graphitization ismany-fold, and most significantly the graphitization process frequentlyallows for the generation of a more ordered crystal lattice in thecarbonaceous particles. A certain improved crystal lattice provides moreregular and uniform structure, and is also believed to improve thecharge capacity of a battery containing the coated carbonaceousparticles described herein. Graphitization also removes impurities. Thispurification step is especially important when impure carbons such asnatural graphite are used as the source of the carbonaceous particles ofthis invention. With regard to appropriate graphitization conditions,again these are to be understood to vary according to the specificnature of the carbonized, coated carbonaceous particles, as well as thereaction conditions required to bring about the graphitization.Generally, the same apparatus used for the carbonization step may alsobe conveniently used, it only being required that such device be capableof further elevating the temperature to a temperature or range oftemperature wherein the effects of graphitization is observed to occur.Typically, graphitization occurs in the temperature range of about 2200°C.-3200° C., although lower or higher temperatures might also be used inthis step. It is required only that a satisfactory degree ofgraphitization be obtained during this step, such that an approvedcharging capacity is achieved. With regard to the process conditions itis desired that it is in an inert atmosphere such as describedpreviously also be present. Graphitization can immediately followcarbonization in which case the carbonized coated carbonaceous particlesare retained in a reaction apparatus, i.e., an oven, and the temperatureis raised up to an appropriate graphitization temperature. With regardto the rate of this temperature rise, desirably this is maintained inthe same rate as that used for the carbonization step although, greateror lesser rates of temperature rise can also be utilized depending uponthe nature of the carbonized, coated carbonaceous particles.

[0043] A key feature of the present invention is in an oxidationreaction which is carried out on the coated particles prior tocarbonization of the coating. The oxidation reaction is believed toprovide certain technical benefits. First, it is believed that thereacted coated particles are relatively infusible following oxidation,which is particularly desirable in view of subsequent process steps, andsubsequent handling of the particles. Second, it is believed that thereacted coated particles are endowed with a surface which yields highefficiency when used as an electrode, particularly when the reactedcoated particles are used in an anode material in a rechargeable storagecell, particularly in a rechargeable Li-ion cell.

[0044] A further aspect of the invention contemplates the use of thecarbonized, and graphitized coated carbonaceous particles in electrodes,particularly anodes, of electrical storage cells, particularly inrechargeable batteries. According to this aspect of the invention, thereis contemplated a method for the manufacture of an electrical storagecell which comprises the step of: incorporating into an anode of theelectrical storage cell coated carbonaceous particles comprising coatedcarbonaceous particles having a coating layer formed of an oxidized,carbon residue forming material.

[0045] According to this aspect of the invention, the coatedcarbonaceous particles produced from the processes described above areformed using the conventional techniques into electrodes, particularlyanodes. While not described with particularity herein, it iscontemplated that known-art manufacturing techniques for the assemblageof such electrodes, as well as known-art devices which facilitate in theformation of such electrodes can be used. A particular advantage whichis obtained by the use of the coated carbonaceous particles taughtherein lies in the fact that due to their coating, they rarely fusetogether thus resulting in a flowable powder. Such flowable powder notonly facilitates in the transport of the carbonized coated carbonaceousmaterials, but also aids in the ultimate electrode as such provides agood degree of packing and uniformity. Such a good degree of packing ofcourse very favorably impacts on the volumetric capacity of any battery,particularly a rechargeable battery of which these electrodes form apart, as, an increased charge carrying capacity per unit volume of theelectrode permits for the decrease in the overall size of a batterywhile maintaining good performance characteristics thereof.

[0046] Another aspect of the current invention is that the coatedcarbonaceous particles of this invention have a very high first cycleefficiency. This high efficiency is developed by the process of thisinvention. First cycle efficiency of the coated carbonaceous particlesof this invention are typically >90%. By comparison, first cycleefficiency is as low as 50% in the carbonaceous particles before coatingand is typically 90% or less in coated particles by other techniques.

[0047] Another aspect of the present invention is an increase ingravimetric or specific capacity as a result of practicing the coatingprocess. Specific capacity is typically increased by 2 to 5% in thegraphitized coated particles of this invention.

[0048] Aspects of the present invention, including certain preferredembodiments are described in the following Examples of the presentinvention.

EXAMPLES Example 1

[0049] Production of Fine Carbonaceous Particles

[0050] A “green” granular needle coke was first milled with a hammermill, and subsequently milled into a fine powder with a jet mill.Subsequently, the resultant milled carbonaceous particles wereclassified to remove particles smaller than 1 μm. The resultantcarbonaceous powder had particles sized in the range of between 1 μm andabout 50 μm, and an average particle size of about 20 μm.

[0051] Production of Coated Carbonaceous Powder Particles

[0052] To a laboratory beaker was provided 4 g of a low melting pointisotropic petroleum pitch (210° C. Mettler softening point, 75% carbonresidue, <100 ppm ash isotropic petroleum pitch.) in 4 g of tetralin(C₁₀H₁₂) at 140° C. In a second laboratory beaker was combined 20 g ofthe carbonaceous powder produced as described previously with 700 ml ofxylene (C₆H₄(CH₃)₂) at 120° C. To the contents of the second beaker wasgradually added the contents of the first beaker, and following theaddition the resultant mixture was heated and maintained at 128° C. for15 minutes under continuous stirring. Subsequently the heat source wasremoved, and while the continuous stirring was maintained the mixturewas allowed to cool to ambient temperature (approx. 20° C.). Theresultant solids were removed from the cooled mixture by first filteringthe mixture on a vacuum funnel, and thereafter drying under vacuum at120° C. for at least 3 hours. Due to the differences in solubility ofthe pitch in tetralin as opposed to the solubility of pitch in xylene atdifferent temperatures, selective precipitation of higher melting pointpitch could precipitate and deposit upon the carbonaceous powderparticles. The final weight of the dried coated carbonaceous powderparticles was about 21.1 g.

[0053] The amount of precipitated pitch on the carbonaceous powder wasdetermined from the following equation:

(Final weight−initial weight)/Final Weight=amount of precipitated pitch

[0054] Therefore, the amount of precipitated pitch on the carbonaceouspowder was established to account for 5 wt %. of the total mass of thecoated carbonaceous powder particles.

[0055] A separate experiment was performed to determine the meltingpoint and carbon residue yield of the coating produced by this Example.An identical solution of isotropic pitch in tetralin was added to anidentical amount of xylene except that there was no carbonaceous pitchdispersed in the xylene. The pitch precipitate that formed had a meltingpoint of 310° C. and exhibited a carbon residue amount of 84%.

[0056] Subsequently the coated carbonaceous powder of Example 1 wasoxidized by thoroughly mixing the powder with 9 g of 1.5 wt % aqueoussolution of NaNO₃ (A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture wassubsequently dried under vacuum at 80° C. and thereafter the driedmixture was then transferred to 50 ml alumina crucibles and insertedinto a vacuum furnace. The crucibles were then slowly heated undervacuum conditions from about ambient temperature to 325° C. at a rate of1° C./minute, at which point the crucibles were maintained under vacuumat 325° C. for 2 hours. This slow heating step provided suitableoxidation reaction conditions whereby the deposited coating could beoxidized and stabilized prior to any further processing steps orhandling, and permitted the pitch coating to form a better orderedmolecular structure. Following this oxidation step, the stabilizedcoated carbonaceous powder particles could then be carbonized at stillhigher temperature(s) with little or no change in their morphology andwith little or no likelihood of the melting of the coating layer.

[0057] Although the stabilized coated carbonaceous powder particlescould be used without further processing, according to preferredembodiments of the invention further process steps were practiced inorder to ultimately graphitize the particles.

[0058] Following the heat conditioning step at 325° C. for 2 hours, thecrucibles containing the stabilized coated carbonaceous powder particleswere further heated in argon gas at a rate of 1° C./minute to atemperature of 350° C. at which point the crucibles were maintained at350° C. for 2 hours. Thereafter the crucibles containing the stabilizedcoated carbonaceous powder particles were further heated at a rate of 1°C./minute to a temperature of 410° C. at which point the crucibles weremaintained at this higher temperature for 2 hours. Subsequently thecrucibles containing the stabilized coated carbonaceous powder particleswere further heated at a rate of 5° C./minute to a temperature of 850°C. at which point the crucibles were maintained at 850° C. for 2 hours,after which heating of the oven was discontinued, the contents of theoven were allowed to cool to ambient temperature (approx. 20° C.). Also,it is to be understood that stabilized coated carbonaceous powderparticles could be used after one or more heat treatments steps andwithout further processing, but according to preferred embodiments ofthe invention the particles are ultimately graphitized.

[0059] After the coated carbonaceous powder particles were cooled, theywere graphitized by transferring them to a graphite crucible and thenintroducing the crucible to an induction furnace having an argonatmosphere, and first heating the crucible at a rate of 13° C./minute toa temperature of 2800° C. and thereafter heating the crucibles at a rateof 5° C./minute to 3000° C. at which time the temperature of theinduction furnace was maintained at 3000° C. for a period of 45 minutes,after which graphitization was believed to be essentially complete.Subsequently the graphitized coated carbonaceous powder particles wereremoved from the crucibles.

[0060] The resultant powder particles demonstrated good powderflowability, and it did not appear that fusion of particles had takenplace.

Example 2

[0061] A further sample of coated carbonaceous powder particles wasproduced in accordance with the process steps described above withreference to Example 1. According to this example however, initiallythere was provided to the first laboratory beaker 8.5 g of the lowmelting point isotropic petroleum pitch described in Example 1, whichwas added to 8.5 g of tetralin (C₁₀H₁₂) at 140° C. The contents of thesecond laboratory beaker remained the same as in Example 1, but theresultant dried coated carbonaceous powder particles recovered exhibiteda final dried weight of about 22.3 grams. Based on this information, thecoating on the coated carbonaceous powder particles was determined to beabout 10% wt. based on the total mass of the coated carbonaceous powderparticles. These dried particles were then subsequently thoroughly mixedwith 9 g of 3.8 wt % aqueous solution of NaNO₃ (A.C.S. reagent, ex. J.T. Baker, Inc.) The mixture was subsequently dried under vacuum at 80°C. The dried mixture was subsequently oxidized, and heat treated inaccordance with the steps described in Example 1, until graphitizedcoated carbonaceous powder particles were obtained. The resultant powderparticles demonstrated good powder flowability, and it did not appearthat fusion of particles had taken place.

Example 3

[0062] A further sample of coated carbonaceous powder particles wasproduced in accordance with the process steps described above withreference to Example 1. According to this example however, there wasprovided 10 g of the low melting point isotropic petroleum pitchdescribed in Example 1, which was added to 10 g of tetralin (C₁₀H₁₂) at140° C. in the first laboratory beaker. The contents of the secondlaboratory beaker remained the same as in Example 1, but the resultantdried coated carbonaceous powder particles recovered exhibited a finaldried weight of about 22.7 grams. Based on this information, the coatingon the coated carbonaceous powder particles was determined to be about12% wt. based on the total mass of the coated carbonaceous powderparticles. These dried particles were then subsequently thoroughly mixedwith 9 g of 4.5 wt % aqueous solution of NaNO₃ (A.C.S. reagent, ex.J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80°C. The dried mixture was subsequently oxidized, and heat treated inaccordance with the steps described in Example 1, until graphitizedcoated carbonaceous powder particles were obtained. The resultant powderparticles demonstrated good powder flowability, and it did not appearthat fusion of particles had taken place.

Example 4

[0063] A further sample of coated carbonaceous powder particles wasproduced in accordance with the process steps described above withreference to Example 1. According to this example however, to the firstlaboratory beaker was provided 15 g of the low melting point isotropicpetroleum pitch of Example 1, and 15 g of tetralin (C₁₀H₁₂) at 140° C.The contents of the second laboratory beaker remained the same as inExample 1, but the resultant dried coated carbonaceous powder particlesrecovered exhibited a final dried weight of about 24 grams. Based onthis information, the coating on the coated carbonaceous powderparticles was determined to be about 17% wt. based on the total mass ofthe coated carbonaceous powder particles. These dried particles werethen subsequently thoroughly mixed with 10 g of 6.0 wt % aqueoussolution of NaNO₃ (A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture wassubsequently dried under vacuum at 80° C. The dried mixture wassubsequently oxidized, and heat treated in accordance with the stepsdescribed in Example 1, until graphitized coated carbonaceous powderparticles were obtained. The resultant powder particles demonstratedgood powder flowability, and it did not appear that fusion of particleshad taken place.

Example 5

[0064] A further sample of coated carbonaceous powder particles wasproduced in accordance with the process steps described above withreference to Example 1. According to this example however, to the firstlaboratory beaker was provided 20 g of the low melting point isotropicpetroleum pitch of Example 1, and 20 g of tetralin (C₁₀H₁₂) at 140° C.The contents of the second laboratory beaker remained the same as inExample 1, but the resultant dried coated carbonaceous powder particlesrecovered exhibited a final dried weight of about 25.3 grams. Based onthis information, the coating on the coated carbonaceous powderparticles was determined to be about 21% wt. based on the total mass ofthe coated carbonaceous powder particles. These dried particles werethen subsequently thoroughly mixed with 10 g of 8 wt % aqueous solutionof NaNO₃ (A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture wassubsequently dried under vacuum at 80° C. The dried mixture wassubsequently oxidized, and heat treated in accordance with the stepsdescribed in Example 1, until graphitized coated carbonaceous powderparticles were obtained. The resultant powder particles demonstratedgood powder flowability, and it did not appear that fusion of particleshad taken place.

Comparative Example 1

[0065] As a comparative example, the same milled green needle cokecarbonaceous powder of Example 1 was graphitized and tested as an anodecarbon in a lithium ion battery. This comparative example demonstratedthe use of an uncoated graphitized carbonaceous powder particles.

[0066] Graphitization of these uncoated carbonaceous powder particleswas achieved by transferring them to a graphite crucible, inserting thecrucible to an induction furnace having an argon atmosphere, and firstheating the crucible at a rate of 13° C./minute to a temperature of2800° C. and thereafter heating the crucible at a rate of 5° C./minuteto 3000° C. at which time the temperature of the induction furnace wasmaintained at 3000° C. for a period of 45 minutes. Subsequent to theseheating steps graphitization was believed to be essentially complete.The crucibles containing the uncoated carbonaceous powder particles wasthen allowed to cool to ambient temperature, after which the powderparticles were removed from the crucibles.

[0067] The resultant uncoated powder particles demonstrated good powderflowability.

Comparative Example 2

[0068] As a further comparison example there were utilized 20 grams of“as-milled” uncoated “green” carbonaceous particles, which were mixed ina laboratory beaker with 9 g of a 1.5 wt % aqueous solution of NaNO₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently driedunder vacuum at 80° C. and thereafter the dried mixture was thenprovided to alumina crucibles and inserted into a vacuum furnace. Thesesamples were subsequently subjected to the same heat treatment steps asoutlined in Example 1, namely, heated under vacuum conditions from aboutambient temperature to 325° C. at a rate of 1° C./minute, and thereaftermaintained under vacuum at 325° C. for 2 hours. Next, the particles werefurther heated under argon at a rate of 1° C./minute to 350° C., andthereafter maintained at 350° C. for 2 hours and subsequently heated ata rate of 1° C./minute to a temperature of 410° C. and thereaftermaintained under vacuum for 2 hours. Subsequently the cruciblescontaining these uncoated carbonaceous powder were further heated underargon at a rate of 5° C./minute to a temperature of 850° C. and thenmaintained at 850° C. for 2 hours, after which heating was discontinued,the contents of the oven were allowed to cool to ambient temperature(approx. 20° C.).

[0069] Graphitization of these uncoated carbonaceous powder particleswas achieved by the same process described above with reference toComparative Ex. 1. Again, the resultant uncoated powder particlesdemonstrated good powder flowability.

[0070] Evaluation of Electrical Capacity

[0071] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles according toExamples 1-5, as well as Comparative Examples 1 and 2 were evaluated bythe following techniques.

[0072] Samples of a powder particle (5 g) were first thoroughly mixedwith 3.82 grams of a solution of 0.382 g of polyvinylidene fluoride(PVDF, ex. Aldrich Chemical Co., Inc.) and 3.44 g of1-methyl-pyrrolidinone (NMP, ex. Aldrich Chemical Co., Inc.) to whichwas also added 0.082 g of acetylene black (having an effective surfacearea of 80 m 21 g, ex. Alfa Aesar) in order to form uniform slurry. Thisslurry was then manually cast utilizing a doctor blade to form a thinfilm having a loading of about 10 mg/cm² onto the rough side of anelectrodeposited copper foil (10 μm, ex. Fuduka Metal Foil & Powder Co.,Ltd.) The cast film was then dried on a hot plate at approx. 100° C. andpressed to a desired density (approx. 1.4 g/cm²) with a roll press.After the cast film was allowed to cool, a disc having an area of 1.5cm² was then punched out from the film and weighed to determine theamount of the graphite powder. Subsequently this disc was further driedunder vacuum at a temperature of 80° C. for approximately 15 minutes,and then the disc was transferred into a sealed box without exposing thedisc to ambient air. The sealed box was filled with ultra-pure argon gashaving oxygen and moisture levels of less than 1 ppm.

[0073] Subsequently the disc was used as the anode in the manufacture ofa standard coin cell (2025 size) which was used as the test cell. Theother electrode of the test cell was a foil of pure lithium (100 μm, ex.Alfa Aesar). A two layer separator was used in the test cell, a glassmat (GF/B Glass Microfibre Filter, ex. Whatman International Ltd.) asthe first layer on the carbon electrode side, and a porous polypropylenefilm (available as Celgard® 2300, ex. Celgard Inc.). as the second layeron the lithium foil. The electrolyte of the test cell was a 1 M LiPF₆ inethylene carbonate (EC)/diethyl carbonate (DEC)/dimethyl carbonate (DMC)solvent mixture (40/30/30) (available as specified by EM Industrial.)Test cells were produced utilizing the component described aboveaccording to conventional techniques, although the samples of powderparticles were varied to ensure that at least one sample coin cell wasproduced incorporating a powder particle sample according to either oneof the demonstrative examples, or according to one of the comparativeexamples. These powders were tested as the anode material in a coin cellconfiguration of carbon/separator/lithium metal at room temperature(˜25° C.). Two or three cells were made for each sample, the reportedcharge capacity and charge efficiency were the average value of thecells.

[0074] The capacity and charging efficiency of a specific powderparticle sample was determined according to the following protocol.Utilizing a standard electrochemical test station (Model BT-2043, ArbinInstrument Corp.) an assembled test cell was first discharged at 1 mA(approx. 67 mA/g) to 0 volts and held at 0 volts for 2 hours or tillcurrent dropped to less than 50 μA whichever occurred first. Thereafterthe assembled test cell was charged at 1 mA to 2 volts during which timethe charge passed during charging was used to calculate the specificcapacity of the graphite powder, while the ratio of the total chargepassed during charging to the total charge passed during discharging wasused to determine the first cycle efficiency.

[0075] Table 1 reports the test results for the seven samples of powderparticles according to each of Examples 1-5, and each of ComparativeExamples 1-2. TABLE 1 Irreversible Coated Capacity capacity lossEfficiency pitch (%) (mAh/g) (mAh/g) (%) Comp. 1  0 314 301 51 Comp. 2 0 304 249 55 Ex. 1  5 322 166 66 Ex. 2 10 337  14 96 Ex. 3 12 330  1496 Ex. 4 17 322  13 96 Ex. 5 21 318  13 96

[0076] It can been seen that the first cycle efficiency is greatlyimproved from 50% to 96% when the amount of coated pitch was increasedto 10 wt %. The table also shows that the efficiency does not increasefurther when it reaches about 96%. In addition, the materials treatedaccording to this invention yield a higher capacity than those that werenot treated.

Example 6

[0077] A further sample of coated carbonaceous powder particlesaccording to the invention was produced utilizing a commerciallyavailable milled synthetic graphite powder having particles sized lessthan 44 μm. (available as KS-44, ex. Lonza). To a first laboratorybeaker was provided 8.5 g of athe low melting point isotropic petroleumpitch of Example 1 in 10 g of tetralin (C₁₀H₁₂) at 140° C. A sample of20 grams of the milled natural graphite powder particles were providedto a second laboratory beaker which contained 700 ml of xylene(C₆H₄(CH₃)₂) at 120° C. To the contents of the second beaker wasgradually added the contents of the first beaker, and following theaddition the resultant mixture was heated and maintained at 128° C. for15 minutes under continuous stirring. Thereafter the heat source wasremoved, and while the continuous stirring was maintained the mixturewas allowed to cool to ambient temperature (approx. 20° C.). Theresultant solids were removed from the cooled mixture by first filteringthe mixture on a vacuum funnel, and thereafter drying under vacuum at120° C. for at least 3 hours. As discussed in Example 1, due to thedifferences in solubility of the pitch in tetralin as opposed to thesolubility of pitch in xylene at different temperatures, selectiveprecipitation of higher melting point pitch could precipitate anddeposit upon the carbonaceous powder particles. The final weight of thedried coated carbonaceous powder particles was determined to be about22.3 g, while the amount of precipitated pitch on the carbonaceouspowder was determined to be 10% wt. of the total mass of the coatedcarbonaceous powder particles.

[0078] Subsequently the dried coated carbonaceous powder particles werethoroughly mixed with 9 g of 3.8 wt % aqueous solution of NaNO₃ (A.C.S.reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried undervacuum at 80° C. The dried mixture was subsequently subjected to thesame heat treatment steps as outlined in Example 1, namely, heated undervacuum conditions from about ambient temperature to 325° C. at a rate of1° C./minute, and thereafter maintained under vacuum at 325° C. for 2hours. Next, the particles were further heated under argon at a rate of1° C./minute to 350° C., and thereafter maintained at 350° C. for 2hours and subsequently heated at a rate of 1° C./minute to a temperatureof 410° C. and thereafter maintained for 2 hours. Subsequently thecrucibles containing the coated carbonaceous powder was were furtherheated at a rate of 5° C./minute to a temperature of 850° C. and thenmaintained at 850° C. for 2 hours, after which heating was discontinued,and the contents of the oven were allowed to cool to ambient temperature(approx. 20° C.).

[0079] Graphitization of these coated carbonaceous powder particles wasachieved by transferring them to a graphite crucible, inserting thecrucible into an induction furnace having an argon atmosphere, and firstheating the crucible at a rate of 13° C./minute to a temperature of2800° C. and thereafter heating the crucible at a rate of 5° C./minuteto 3000° C. at which time the temperature of the induction furnace wasmaintained at 3000° C. for a period of 45 minutes. Subsequent to theseheating steps graphitization was believed to be essentially complete.The crucibles containing the coated carbonaceous powder particles wasthen allowed to cool to ambient temperature, after which the powderparticles were removed from the crucibles. The resultant powderparticles exhibited good flowability.

[0080] A sample of the coated carbonaceous powder particles producedaccording to this example was evaluated for their electrical performancecharacteristics utilizing the procedure described above under theheading “Evaluation of electrical capacity”. The results of theelectrical performance evaluation are described on Table 2, following.

Example 7

[0081] A further sample of coated carbonaceous powder particlesaccording to the invention was produced utilizing particles derived froma calcined petroleum needle coke (calcining temperature 1100° C.) havingparticles sized in the range of between 1 μm and about 50 μm, and anaverage particle size of about 20 μm. Similarly to the process describedin Example 6, to a first laboratory beaker was provided 8.5 g of the lowmelting point isotropic petroleum pitch of Example 1 in 8.5 g oftetralin (C₁₀H₁₂) at 140° C. A sample of 20 grams of the milled calcinedpetroleum coke powder particles were provided to a second laboratorybeaker which contained 700 ml of xylene (C₆H₄(C₂H₃)₂) at 120° C. To thecontents of the second beaker was gradually added the contents of thefirst beaker, and following the addition the resultant mixture washeated and maintained at 128° C. for 15 minutes under continuousstirring. Thereafter the heat source was removed, and while thecontinuous stirring was maintained the mixture was allowed to cool toambient temperature (approx. 20° C.). The resultant solids were removedfrom the cooled mixture by first filtering the mixture on a vacuumfunnel, and thereafter drying under vacuum at 120° C. for at least 3hours. As discussed in Example 1, due to the differences in solubilityof the pitch in tetralin as opposed to the solubility of pitch in xyleneat different temperatures, selective precipitation of higher meltingpoint pitch could precipitate and deposit upon the carbonaceous powderparticles. The final weight of the dried coated carbonaceous powderparticles was determined to be about 22.3 g, while the amount ofprecipitated pitch on the carbonaceous powder was determined to be 10%wt. of the total mass of the coated carbonaceous powder particles.

[0082] Subsequently the dried coated carbonaceous powder particles werethoroughly mixed with 9 g of 3.8 wt % aqueous solution of NaNO₃ (A.C.S.reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried undervacuum at 80° C. The dried mixture was subsequently subjected to thesame heat treatment steps as outlined in Example 6, including the finalgraphitization process. The resultant powder particles exhibited goodflowability.

[0083] A sample of the coated carbonaceous powder particles producedaccording to this example was evaluated for their electrical performancecharacteristics utilizing the procedure described above under theheading “Evaluation of electrical capacity”. The results of theelectrical performance evaluation are described on Table 2, following.

Example 8

[0084] A still further sample of coated carbonaceous powder particlesaccording to the invention was produced utilizing a different milled“green” petroleum needle coke having particles sized in the range ofbetween 1 μm and about 50 μm, and an average particle size of about 20μm. Similarly to the process described in Example 6, to a firstlaboratory beaker was provided 10 g of the low melting point isotropicpetroleum pitch of Example 1 in 10 g of tetralin (C₁₀H₁₂) at 140° C. Asample of 20 grams of the milled natural graphite powder particles wereprovided to a second laboratory beaker which contained 700 ml of xylene(C₆H₄(C₂H₃)₂) at 120° C. To the contents of the second beaker wasgradually added the contents of the first beaker, and following theaddition the resultant mixture was heated and maintained at 128° C. for15 minutes under continuous stirring. Thereafter the heat source wasremoved, and while the continuous stirring was maintained the mixturewas allowed to cool to ambient temperature (approx. 20° C.). Theresultant solids were removed from the cooled mixture by first filteringthe mixture on a vacuum funnel, and thereafter drying under vacuum at120° C. for at least 3 hours. As discussed in Example 1, due to thedifferences in solubility of the pitch in tetralin as opposed to thesolubility of pitch in xylene at different temperatures, selectiveprecipitation of higher melting point pitch could precipitate anddeposit upon the carbonaceous powder particles. The final weight of thedried coated carbonaceous powder particles was determined to be about 23g, while the amount of precipitated pitch on the carbonaceous powder wasdetermined to be 13% wt. of the total mass of the coated carbonaceouspowder particles.

[0085] Subsequently the dried coated carbonaceous powder particles werethoroughly mixed with 9 g of 4.5 wt % aqueous solution of NaNO₃ (A.C.S.reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried undervacuum at 80° C. The dried mixture was subsequently subjected to thesame heat treatment steps as outlined in Example 6, including the finalgraphitization process. The resultant powder particles exhibited goodflowability.

[0086] A sample of the coated carbonaceous powder particles producedaccording to this example was evaluated for its electrical performancecharacteristics utilizing the procedure described above under theheading “Evaluation of electrical capacity”. The results of theelectrical performance evaluation are described on Table 2, following.

Comparative Example 3

[0087] For comparative purposes a sample of the commercially availablemilled synthetic graphite powder as described in Example 6 was alsoevaluated for its electrical performance characteristics utilizing theprocedure described above under the heading “Evaluation of electricalcapacity”. The sample of the available milled synthetic graphite powderwas used as obtained, and was not treated according to the presentinventive process. The results of the electrical performance evaluationare described on Table 2, following.

Comparative Example 4

[0088] For comparative purposes a sample of milled calcined petroleumneedle coke as described in Example 7 was also evaluated for itselectrical performance characteristics utilizing the procedure describedabove under the heading “Evaluation of electrical capacity”. The sampleof the available milled calcined coke was heat-treated in the same wayas the coated carbonaceous particles of Example 7. The results of theelectrical performance evaluation on the resultant graphite powder aredescribed on Table 2, following.

Comparative Example 5

[0089] For comparative purposes a sample of milled “green” needle cokeas described in Example 8 was also evaluated for its electricalperformance characteristics utilizing the procedure described aboveunder the heading “Evaluation of electrical capacity”. The sample of theavailable milled “green” coke was used as obtained, and was not treatedaccording to the coating steps of the present inventive process. Theuncoated coke powder was heated to form a graphite powder in the sameway as in Example 8. The results of the electrical performanceevaluation are described on Table 2, following. TABLE 2 IrreversibleCapacity capacity loss Efficiency Coated pitch (mAh/g) (mAh/g) (%) (%)Ex. 6 344  22 94 10 Ex. 7 333  14 96 10 Ex. 8 341  14 96 13 Comp. Ex. 3353  48 88  0 Comp. Ex. 4 304 386 44  0 Comp. Ex. 5 304 403 43  0

[0090] As is readily seen from the results reported in Table 2, thecompositions according to the invention (Examples 6, 7 and 8) exhibiteda high efficiency (>94%). The comparison examples and their untreatedmaterials suffered from a much lower efficiency than the materialstreated according to this invention, as well as suffering from a higherirreversible capacity loss.

Example 9

[0091] A further sample of coated carbonaceous powder particlesaccording to the invention was produced according to an alternatetechnique for providing the coating to the particles.

[0092] In a laboratory beaker was provided 20 g of the low melting pointisotropic petroleum pitch of Example 1 to 80 grams of1-methyl-pyrrolidinone (NMP, ex. Aldrich Chemical Co., Inc.) to form a20% wt. solution of the petroleum pitch. The solution was heated toapprox. 60° C. under stirring, at which time 20 g of the milled “green”needle coke particles of Example 8 were introduced, and the contents ofthe beakers were stirred for a further 15 minutes to ensure homogeneity.Subsequently, resultant solids were removed from the mixture by firstfiltering the mixture utilizing a vacuum funnel, and thereafter dryingunder vacuum at 100° C. for at least 5 hours. The final weight of thedried coated carbonaceous powder particles was determined to be about23.5 g, while the amount of precipitated pitch on the carbonaceouspowder was determined to be 15% wt. of the total mass of the coatedcarbonaceous powder particles.

[0093] The dried coated carbonaceous powder particles were nextthoroughly mixed with 12 g of 3 wt % aqueous solution of NaNO₃ (A.C.S.reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried undervacuum at 80° C. and thereafter the dried mixture was then provided to50 cc alumina crucibles and inserted into a vacuum furnace. Thereafterthe coated carbonaceous powder particles were subjected to the same heattreatment steps as described in Example 1, and ultimately graphitizedcoated carbonaceous powder particles were produced.

[0094] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 3, following. TABLE 3 IrreversibleCapacity capacity loss Efficiency (mAh/g) (mAh/g) (%) Ex. 9 339 29 92

Example 10

[0095] A further sample of coated carbonaceous powder particlesaccording to the invention was produced according to an alternatetechnique for providing the coating to the particles.

[0096] In a laboratory beaker was provided 20 g of the low melting pointisotropic petroleum pitch of Example 1 to 80 g of 1-methyl-pyrrolidinone(NMP, ex. Aldrich Chemical Co., Inc.) to form a 20% wt. solution of thepetroleum pitch. The solution was heated to approx. 60° C. understirring, at which time 20 g of the particulate calcined petroleum cokeof Example 7 were introduced, and the contents of the beaker was stirredfor a further 15 minutes to ensure homogeneity. Subsequently, resultantsolids were removed from the mixture by first filtering the mixtureutilizing a vacuum funnel, and thereafter drying under vacuum at 100° C.for at least 5 hours. The final weight of the dried coated carbonaceouspowder particles was determined to be about 21 g, while the amount ofprecipitated pitch on the carbonaceous powder was determined to be 5%wt. of the total mass of the coated carbonaceous powder particles.

[0097] The dried coated carbonaceous powder particles were nextthoroughly mixed with 11 g of 3 wt % aqueous solution of NaNO₃ (A.C.S.reagent, ex. J.T.Baker, Inc.). The mixture was subsequently dried undervacuum at 80° C. and thereafter the dried mixture was then provided toalumina crucibles and inserted into a vacuum furnace. Thereafter thecoated carbonaceous powder particles were subjected to the same heattreatment steps as described in Example 1, and ultimately graphitizedcoated carbonaceous powder particles were produced.

[0098] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 4, following. TABLE 4 IrreversibleCoated pitch Capacity capacity loss Efficiency (%) (mAh/g) (mAh/g) (%)Ex. 10 5 343 22 94

[0099] As this example illustrated, a pitch coating level as little as 5wt % on coke powder or coated carbon residue as little as 4 wt % stillsignificantly suppresses the irreversible capacity loss according tothis invention.

Example 11

[0100] A sample of coated carbonaceous powder particles according to theinvention was produced demonstrating the use of lignin as the fusible,carbon residue forming material coating for carbonaceous powderparticles. Additionally this example demonstrates a one-step coating andoxidation process.

[0101] In a laboratory beaker 2.0 g of lignin (Alkali Kraft, ex AldrichChemicals Co. Inc.) and 0.3 g of NaNO₃ were mixed in 9 g of 1 M KOHaqueous solution. This lignin has a carbon residue of about 47% andmelting point of 300° C. Subsequently to the laboratory beaker wasprovided 20 g of the comminuted “green” granular coke particles asprepared used in Example 1, and the contents of the laboratory beakerwere thoroughly mixed in a laboratory blender (Waring Commercialblender, Model 51BL31). Thereafter the mixture was removed from thelaboratory blender, dried at 80° C. under vacuum for 12 hours. The finalweight of the dried coated carbonaceous powder particles was determinedto be about 22.4 g, while the amount of precipitated lignin on thecarbonaceous powder was determined to be 10 wt % of the total mass ofthe coated carbonaceous powder particles.

[0102] Subsequently the dried coated carbonaceous powder particles weresubjected to the same heat treatment steps as described in Example 1,and ultimately graphitized coated carbonaceous powder particles wereproduced.

[0103] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 5, following. TABLE 5 IrreversibleCoated Capacity capacity loss Efficiency lignin (%) (mAh/g) (mAh/g) (%)Ex. 11 10 330 21 94

[0104] The efficiency of the composition according to Example 11demonstrate a significant and surprising improvement over the resultsreported for Comparative Example 5 on Table 2, demonstrating thesurprising improvements achieved by the practice of the presentinvention.

Example 12

[0105] A sample of coated carbonaceous powder particles according to theinvention was produced demonstrating the use of table sugar as thefusible, carbon residue forming material coating for carbonaceous powderparticles. This sugar has a carbon residue of about 25%.

[0106] In a laboratory beaker 3 grams of table white sugar (HouseRecipe®, distributed by Sysco Corporation) and 0.3 grams of NaNO₃ weredissolved in 9 grams of de-ionized water. Subsequently to the laboratorybeaker was provided 20 g of the comminuted “green” granular cokeparticles as prepared used in Example 1, and the contents of thelaboratory beaker were thoroughly mixed in a laboratory blender (WaringCommercial blender, Model 51BL31). Thereafter mixture was removed fromthe laboratory beaker, dried under vacuum at 80° C. for 3 hours. Theamount of coated sugar on the coke particles was determined to be about13 wt %.

[0107] Subsequently the dried coated carbonaceous powder particles weresubjected to the same heat treatment steps as described in Example 1,and ultimately graphitized coated carbonaceous powder particles wereproduced.

[0108] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 6, following. TABLE 6 IrreversibleCoated sugar Capacity capacity loss Efficiency (%) (mAh/g) (mAh/g) (%)Ex. 12 13 303 23 93

Example 13

[0109] A sample of coated carbonaceous powder particles according to theinvention was produced demonstrating the use of ambient air as theoxidizing agent for the fusible, carbon residue forming material coatingof carbonaceous powder particles.

[0110] To a laboratory beaker was provided 8.5 g of the low meltingpoint isotropic petroleum pitch of Example 1 in 8.5 g of tetralin(C₁₀H₁₂) at 140° C. In a second laboratory beaker was combined 20 g ofthe carbonaceous powder produced and as described with reference toExample 1 with 700 ml of xylene (C₆H₄(C₂H₃)₂) at 120° C. To the contentsof the second beaker was gradually added the contents of the firstbeaker, and following the addition the resultant mixture was heated andmaintained at about 128° C. for 15 minutes under continuous stirring.Subsequently the heat source was removed, and while the continuousstirring was maintained the mixture was allowed to cool to ambienttemperature (approx. 20° C.). The resultant solids were removed from thecooled mixture by first filtering the mixture on a vacuum funnel, andthereafter drying under vacuum at 120° C. for at least 3 hours.

[0111] The dried powder weighed 22.3 g. The amount of precipitated pitchon the carbonaceous powder was determined to account for 10% wt. of thetotal mass of the coated carbonaceous powder particles.

[0112] Thereafter the coated carbonaceous powder particles were placedin a laboratory scale fluidized bed reactor and heated from ambienttemperature at a heating rate of 10° C./minute to 275° C. and held for30 minutes at 275° C. while the coated carbonaceous powder particleswere fluidized using air as the fluidizing gas. Subsequently the reactedpowder particles were transferred into a tube furnace (Linberg/Blue M)and carbonized in pure argon gas by heating from ambient temperature ata heating rate of 5° C./minute to 850° C., and once this temperature wasreached, the coated carbonaceous powder particles were maintained atthis temperature for 2 hours. The coated carbonaceous powder particleswere subsequently withdrawn and allowed to cool.

[0113] Graphitization of the coated carbonaceous powder particles wasachieved by next transferring them to a graphite crucible, inserting thecrucible into an induction furnace having an argon atmosphere, and firstheating the crucible at a rate of 13° C./minute to a temperature of2800° C. and thereafter heating the crucible at a rate of 5° C./minuteto 3000° C. at which time the temperature of the induction furnace wasmaintained at 3000° C. for a period of 45 minutes. Subsequent to theseheating steps graphitization was believed to be essentially complete.The crucibles containing the coated carbonaceous powder particles werethen allowed to cool to ambient temperature, after which the powderparticles were removed from the crucibles. The resultant powderparticles demonstrated good powder flowability, and it did not appearthat fusion of particles had taken place.

[0114] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 7, following. TABLE 7 IrreversibleCoated pitch Capacity capacity loss Efficiency (%) (mAh/g) (mAh/g) (%)Ex. 13 10 330 14 96

Example 14

[0115] A further sample of coated carbonaceous powder particlesaccording to the invention was produced demonstrating the use of ambientair as the oxidizing agent for the fusible, carbon residue formingmaterial coating of carbonaceous powder particles.

[0116] In a laboratory beaker was provided 20 g of the low melting pointisotropic petroleum pitch of Example 1 to 80 g of 1-methyl-pyrrolidinone(NMP, ex. Aldrich Chemical Co., Inc.) to form a 20% wt. solution of thepetroleum pitch. The solution was heated to approx. 60° C. understirring, at which time 20 g of the particlate calcined petroleum cokedescribed in Example 7 was introduced, and the contents of the beakerwas stirred for a further 15 minutes to ensure homogeneity.Subsequently, resultant solids were removed from the mixture by firstfiltering the mixture utilizing a vacuum funnel, and thereafter dryingunder vacuum at 100° C. for at least 5 hours. The final weight of thedried coated carbonaceous powder particles was determined to be about21.5 g, while the amount of precipitated pitch on the carbonaceouspowder was determined to be 7 wt % of the total mass of the coatedcarbonaceous powder particles.

[0117] Thereafter the coated carbonaceous powder particles were placedin a fluidized bed reactor as described in Example 13 and heated fromambient temperature at a heating rate of 10° C./minute to 275° C. andheld for 30 minutes at 275° C. while the coated carbonaceous powderparticles were fluidized using air as the fluidizing gas. Subsequentlythe reacted powder particles were transferred into a tube furnace asdescribed in Example 13 and carbonized in pure argon gas by heating fromambient temperature at a heating rate of 5° C./minute to 850° C., andonce this temperature was reached, the coated carbonaceous powderparticles were maintained at this temperature for 2 hours. The coatedcarbonaceous powder particles were subsequently withdrawn and allowed tocool.

[0118] Graphitization of these coated carbonaceous powder particles wasachieved by next transferring them to a graphite crucible, inserting thecrucible to an induction furnace having an argon atmosphere, and firstheating the crucible at a rate of 13° C./minute to a temperature of2800° C. and thereafter heating the crucible at a rate of 5° C./minuteto 3000° C. at which time the temperature of the induction furnace wasmaintained at 3000° C. for a period of 45 minutes. Subsequent to theseheating steps graphitization was believed to be essentially complete.The crucibles containing the uncoated carbonaceous powder particles werethen allowed to cool to ambient temperature, after which the powderparticles were removed from the crucibles.

[0119] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 8, following. TABLE 8 IrreversibleCoated pitch Capacity capacity loss Efficiency (%) (mAh/g) (mAh/g) (%)Ex. 14 7 334 29 92

Comparative Example 6

[0120] For comparative purposes samples of coated carbonaceous powderparticles which were not subjected to an oxidation reaction step wereprepared by the following protocol.

[0121] To a laboratory beaker was provided 8.5 g of the low meltingpoint isotropic petroleum pitch as described in Example 1 into 8.5 g oftetralin (C₁₀H₁₂) at 140° C. In a second laboratory beaker was combined20 g of the carbonaceous powder produced and as described with referenceto Example 1 with 700 ml of xylene (C₆H₄(CH₃)₂) at 120° C. To thecontents of the second beaker was gradually added the contents of thefirst beaker, and following the addition the resultant mixture washeated and maintained at about 128° C. for 15 minutes under continuousstirring. Subsequently the heat source was removed, and while thecontinuous stirring was maintained the mixture was allowed to cool toambient temperature (approx. 20° C.). The resultant solids were removedfrom the cooled mixture by first filtering the mixture on a vacuumfunnel, and thereafter drying under vacuum at 120° C. for at least 3hours.

[0122] The amount of precipitated pitch on the carbonaceous powder wasdetermined to account for 10% wt. of the total mass of the coatedcarbonaceous powder particles.

[0123] Thereafter the coated carbonaceous powder particles were placedin an alumina crucible, and the crucible was inserted into a tubularfurnace (Linberg/Blue M), and therein heated from ambient temperatureaccording to the following protocol: a first heating rate of 5°C./minute to 200° C. and held at that temperature for 30 minutes,followed by a second heating rate of 2° C./minute to 350° C. and held atthat temperature for 2 hours, next heated at a third heating rate of 5°C./minute to 850° C. and held at that temperature for 2 hours andfinally, cooling the coated carbonaceous powder particles at a rate of5° C./minute to ambient temperature (approx. 20° C.). The recoveredcarbonaceous powder particles were observed to have conglomerated into asingle cake, which was withdrawn from the crucible and first crushedinto smaller pieces and then ball milled into a powder form.

[0124] Graphitization of these coated carbonaceous powder particles wasachieved by next transferring them to a graphite crucible, inserting thecrucible into an induction furnace having an argon atmosphere, and firstheating the crucible at a rate of 13° C./minute to a temperature of2800° C. and thereafter heating the crucible at a rate of 5° C./minuteto 3000° C. at which time the temperature of the induction furnace wasmaintained at 3000° C. for a period of 45 minutes. Subsequent to theseheating steps graphitization was believed to be essentially complete.The crucibles containing the carbonaceous powder particles was thenallowed to cool to ambient temperature (approx. 20° C.), after which thepowder particles were removed from the crucibles.

[0125] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 9, following. TABLE 9 IrreversibleCoated pitch Capacity capacity loss Efficiency (%) (mAh/g) (mAh/g) (%)Comp. Ex. 6 10 300 352 46

[0126] As can be understood from these results, particularly incomparison with the results of Ex. 2, as well as the results reported onTables 7 and 8 where the pitch coated carbonaceous powder particleswhich had not been oxidized, but were simply carbonized in an inertatmosphere resulted in poor electrical charge capacity and poor chargeefficiency.

Comparative Example 7

[0127] For further comparison, samples of coated carbonaceous powderparticles not subjected to an oxidation reaction step were prepared bythe heating protocol used to produce the compositions of ComparativeExample 6. The comparison samples according to the instant ComparativeExample differed in that the coated carbonaceous powder particles wereprepared in the same manner as illustrated in Example 10. Aftercarbonization, it was observed that the carbonaceous powder particleshad conglomerated into a single cake. The carbon powder clump then waswithdrawn from the crucible and first crushed into smaller pieces andthen ball milled into a powder form before graphitization.

[0128] As in the prior Comparative Example's evaluation, the electricalcharge capacity, as well as the irreversible electrical charge capacityloss of the powder particles according to the present ComparativeExample were evaluated utilizing the procedure described above under theheading “Evaluation of electrical capacity”. The results of theelectrical performance evaluation are described on Table 9, following.TABLE 10 Irreversible Coated pitch Capacity capacity loss Efficiency (%)(mAh/g) (mAh/g) (%) Comp. Ex. 7 5 317 106 75

[0129] As can be understood from these results, particularly incomparison with the results of Ex. 10 and the results reported on Tables7 and 8, as well as the perfomance of the pitch coated carbonaceouspowder particles which had not been oxidized, but were simply carbonizedin an inert atmosphere resulted in improved, but still poor electricalcharge capacity as compared to the sample according to ComparativeExample 6.

Example 15

[0130] A further sample of coated carbonaceous powder particlesaccording to the invention was produced demonstrating the use of aliquid oxidizing agent for the fusible, carbon residue forming materialcoating of carbonaceous powder particles.

[0131] To a laboratory beaker was provided 8.5 g of the low meltingpoint isotropic petroleum pitch described in Example 1in 8.5 g oftetralin (C₁₀H₁₂) at 140° C. In a second laboratory beaker was combined20 g of the carbonaceous powder produced and as described with referenceto Example 1 with 700 ml of xylene (C₆H₄(CH₃)₂) at 120° C. To thecontents of the second beaker was gradually added the contents of thefirst beaker, and following the addition the resultant mixture washeated and maintained at about 128° C. for 15 minutes under continuousstirring. Subsequently the heat source was removed, and while thecontinuous stirring was maintained the mixture was allowed to cool toambient temperature (approx. 20° C.). The resultant solids were removedfrom the cooled mixture by first filtering the mixture on a vacuumfunnel, and thereafter drying under vacuum at 120° C. for at least 3hours. The resultant dried coated carbonaceous powder particlesrecovered exhibited a final dried weight of about 22.3 grams. The amountof precipitated pitch on the carbonaceous powder was determined toaccount for 10% wt. of the total mass of the coated carbonaceous powderparticles.

[0132] Next the dried pitch-coated powder was poured into a third beakercontaining a 35% wt. aqueous solution of nitric acid (HNO₃) at 60° C.,and oxidizing agent, and the resulting mixture was maintained at thistemperature while stirring. Thereafter the solids were recovered byfirst filtering the mixture on a vacuum funnel, thoroughly washing thefiltered solids with deionized water and thereafter drying under vacuumat 80° C. for at least 5 hours.

[0133] Subsequently the recovered coated carbonaceous powder particleswere introduced into an alumina crucible and heated in an argonatmosphere from ambient temperature at a rate of 5° C./minute to atemperature of 850° C. at which point the crucibles were maintained atthat temperature for 2 hours, after which the crucibles were allowed tocool at the rate of 5° C./minute to ambient temperature, i.e., 20° C. atwhich point the coated carbonaceous powder particles were removed fromthe crucibles. The resultant powder particles demonstrated good powderflowability, and it did not appear that fusion of particles had takenplace.

[0134] Thereafter the coated carbonaceous powder particles weregraphitized by providing them to a graphite crucible, inserting thecrucible to an induction furnace having an argon atmosphere, and firstheating the crucible at a rate of 13° C./minute to a temperature of2800° C. and thereafter heating the crucible at a rate of 5° C./minuteto 3000° C. at which time the temperature of the induction furnace wasmaintained at 3000° C. for a period of 45 minutes. Subsequent to theseheating steps graphitization was believed to be essentially complete.The crucibles containing the coated carbonaceous powder particles werethen allowed to cool to ambient temperature, after which the powderparticles were removed from the crucibles. The resultant powderparticles demonstrated good powder flowability, and it did not appearthat fusion of particles had taken place.

[0135] The electrical charge capacity, as well as the irreversibleelectrical charge capacity loss of the powder particles were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 11, following. TABLE 11 IrreversibleCoated pitch Capacity capacity loss Efficiency (%) (mAh/g) (mAh/g) (%)Ex. 15 10 330 14 96

Example 16

[0136] Further samples of coated carbonaceous powder particles accordingto the invention were produced which also utilized a liquid oxidizingagent as was used in Example 15. The compositions were prepared by thesame protocol used to produce the compositions of Example 14. Namely,the dried pitch-coated powder prepared as shown in Example 14 wasoxidized in a nitric acid solution as illustrated in Example 15 beforecarbonization and graphitization.

[0137] As in the prior Example's evaluation, the electrical chargecapacity, as well as the irreversible electrical charge capacity loss ofthe powder particles according to the present Example were evaluatedutilizing the procedure described above under the heading “Evaluation ofelectrical capacity”. The results of the electrical performanceevaluation are described on Table 12, following. TABLE 12 IrreversibleCoated pitch Capacity capacity loss Efficiency (%) (mAh/g) (mAh/g) (%)Comp. Ex. 16 7 338 26 93

[0138] The coated carbonaceous powder particles produced according toExamples 15 and 16, and their resultant excellent electrical propertiesdemonstrate the utility of liquid oxidizing agents.

[0139] As is evident from the foregoing, the compositions provided bythe invention provide high capacity and high efficiency carbon materialwhich can be derived from a wide variety of sources. Additionally thecompositions provided by the invention also feature good powderflowability, which is particularly beneficial during any handling ormanufacturing steps necessary to form these materials into usefulelectrodes or into other articles not specifically described herein.

[0140] While described in terms of the presently preferred embodiments,it is to be understood that the present disclosure is to be interpretedas by way of illustration, and not by way of limitation, and thatvarious modifications and alterations apparent to one skilled in the artmay be made without departing from the scope and spirit of the presentinvention.

1. A process for the production of coated carbonaceous particles ofwhich process comprises the steps of: providing particles of acarbonaceous material; providing a coating of a fusible, carbon residueforming material onto the surface of said particles; stabilizing thecoated particles by subjecting said particles to an oxidation reactionusing an oxidizing agent; subsequently carbonizing the coated particles;and, optionally thereafter graphitizing the coated particles.
 2. Theprocess according to claim 1 wherein the carbonaceous particles are apulvurent carbonaceous material selected from the group consisting of:pitches, calcined petroleum cokes, uncalcined petroleum cokes, highlycrystalline cokes, coal tar cokes, synthetic graphites, naturalgraphites, soft carbons derived from organic polymers, and soft carbonsderived from natural polymers.
 3. The process according to claim 2wherein the carbonaceous particles are a pulvurent carbonaceous materialselected from the group consisting of: calcined petroleum cokes,uncalcined petroleum cokes, highly crystalline cokes, syntheticgraphites, and natural graphites.
 4. The process according to claim 1wherein the carbonaceous particles have an average particle size of upto about 150 μm.
 5. The process according to claim 4 wherein thecarbonaceous particles have average particles sizes between about 5 μmand about 70 μm.
 6. The process according to claim 5 wherein thecarbonaceous particles have average particle sizes between about 5 μmand about 45 μm.
 7. The process according to claim 1 wherein the carbonresidue forming material is coated onto the surface of the carbonaceousparticles by liquefying the carbon residue forming material, andcontacting the liquefied carbon residue forming material with the fineparticles of the carbonaceous material.
 8. The process according toclaim 1 wherein the carbon residue forming material is coated onto thesurface of the carbonaceous particles by selectively precipitating acarbon residue forming material onto the carbonaceous particles.
 9. Theprocess according to claim wherein the carbon residue forming materialis coated onto the surface of the carbonaceous particles in amounts ofbetween 1% wt. and 50% wt.
 10. The process according to claim 1 whereinthe carbon residue forming material is coated onto the surface of thecarbonaceous particles in amounts of between 2.5% wt. and 25% wt. 11.The process according to claim 1 wherein the oxidizing agent and thecarbon residue forming material is applied to the fine particles of thecarbonaceous material in a single step.
 12. The process according toclaim 1 wherein the oxidizing agent is a solid oxidizing agent selectedfrom the group consisting of: inorganic and organic oxidizing agents.13. The process according to claim 12 wherein the oxidizing agent isselected from the group consisting of: alkali nitrates and alkalisulfates such as are represented by MNO₃ and M₂SO₄, where M denotesalkali metal; M′O_(x) where M′ represents a transition metal, inorganicsalts, and organic salts.
 14. The process according to claim 1 whereinthe oxidizing agent is a liquid oxidizing agent.
 15. The processaccording to claim 14 wherein the oxidizing agent is selected from thegroup consisting of: oxidizing acids, aqueous solutions containingoxidizing salts, non-aqueous solutions containing oxidizing salts,peroxides and aryl quinones.
 16. The process according to claim 1wherein the oxidizing agent is a gaseous oxidizing agent.
 17. Theprocess according to claim 16 wherein the oxidizing agent is a gaseousoxidizing agent selected from the group consisting of: oxygen, sulfurfumes, gaseous oxides, nitrogen oxide gas, ambient air and halogens. 18.Coated carbonaceous particles having a coating layer formed of anoxidized fusible carbon residue forming material.
 19. Coatedcarbonaceous particles according to claim 18 having a coating layerformed of a graphitized, fusible oxidized carbon residue formingmaterial.
 20. Coated carbonaceous particles according to claim 18 havinga substantially smooth coating.
 21. The coated carbonaceous particlesaccording to claim 18 wherein the carbonaceous particles are a pulvurentcarbonaceous material selected from the group consisting of: petroleumpitches, calcined petroleum cokes, uncalcined petroleum cokes, highlycrystalline cokes, coal tar cokes, synthetic graphites, naturalgraphites, soft carbons derived from organic polymers, and soft carbonsderived from natural polymers.
 22. The coated carbonaceous particlesaccording to claim 18 wherein the fine carbonaceous particles are apulvurent carbonaceous material selected from the group consisting of:calcined petroleum cokes, uncalcined petroleum cokes, highly crystallinecokes, synthetic graphites, and natural graphites.
 23. Coatedcarbonaceous particles comprising coated fine carbonaceous particleshaving a coating layer formed of an oxidized, fusible carbon residueforming material according to claim
 18. 24. An electrical storage cellcomprising coated carbonaceous particles according to claim
 18. 25. Anelectrical storage cell according to claim 24, wherein the electricalstorage cell is a rechargeable electrical storage cell.
 26. A method forthe manufacture of an electrical storage cell which comprises the stepof: incorporating into an anode of the electrical storage cell thecoated carbonaceous particles according to claim
 18. 27. A process forthe production of coated carbonaceous particles having substantiallysmooth coatings formed of an oxidized, carbon residue forming materialwhich process comprises the steps of: providing particles of acarbonaceous material; providing a coating of a fusible, carbon residueforming material onto the surface of said particles by contacting theparticles of the carbonaceous material with a liquid carbon residueforming material; stabilizing the coated particles by subjecting saidparticles to an oxidation reaction using an oxidizing agent;subsequently carbonizing the coated particles; and, optionallythereafter graphitizing the coated particles.
 28. Coated carbonaceousparticles having substantially smooth coatings formed of an oxidized,carbon residue forming material produced by the process of claim
 27. 29.Coated carbonaceous particles having substantially smooth coatingsformed of an oxidized, carbon residue forming material.